CYTOLOGICAL CHANGES IN AGING BACTERIAL CULTURES

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Abstract
Morphological changes occurring in aging broth and agar cultures of Bacillus anthracis were observed with the phase-contrast microscope. In 4 to 5 days in liquid culture cells lost their normal shape and became fusiform or spherical. Chromatin bodies were clearly visible inside the cells at this time. Spontaneous conversion into protoplast-like spherical cells was observed on the 6th or 7th day. These cells were sensitive to osmotic changes but could be preserved by the addition of sucrose to the medium. Budding and atypical multicellular forms also were observed at this stage. In agar cultures the conversion into spherical forms was observed with more regularity; the presence of sucrose in the medium favored the process. In very late stages of growth the sperical cells disintegrated into conglomerated masses of cellular debris with the discrete chromatin bodies enmeshed in them. At this stage secondary colonies appeared superimposed on the primary ones, and on transfer to suitable medium gave rise to unstable L colonies.